Surgical instrument

ABSTRACT

A cutting block comprises a body having a top surface for guiding a saw blade, and a top plate connected to the body. The top plate can move between a first position in which the top plate is spaced apart from the body and a second position in which the top surface of the top plate is an extension of the top surface of the body. The top plate has first and second resiliently deformable arms extending from it, spaced apart along the top plate, and the body has first and second recesses formed in it extending substantially perpendicularly to the top surface of the body. The first and second arms on the top plate are inserted in the recesses so that the arms and the recesses define the path for movement of the top plate relative to the body between the first and second position.

The present invention relates to surgical instruments and in particularto surgical instruments that include guiding surfaces for saws and othercutting tools used in bone surface preparation.

Many surgical instruments are fixed in a known position relative to apatient, particularly when used in bone surface preparation. One exampleis a cutting block. Cutting blocks are typically affixed to a patient'sbone in a position such that they can guide cutting and resection of thebone surface for receiving an implant.

Existing cutting blocks may include a guide, recess or cutting groovefor the cutting tool, such as a saw, used for cutting and resectioningin order to correctly position and guide the cutting tool during thesurgical procedure.

In an existing cutting block, the cutting block has a top surface forguiding a saw blade during a step in an orthopaedical surgicalprocedure, such as distal femoral resection. The cutting block alsoincludes a top plate which defines a cutting groove for receiving thesaw and which can also be used as a guide during distal femoralresectioning. To achieve this, the top plate is movable between anextended, first position to a closed, second position. In the firstposition, the top plate defines the cutting groove. When the top plateis in the second position, the top plate is contiguous with a main bodyof the cutting block to define a top, distal surface for guiding thecutting tool. A surgeon can use either the top surface or the cuttinggroove as a guide for the cutting tool. The choice of either the topsurface or the cutting groove is usual one of personal preference forthe surgeon.

Historically, the top plate is locked into the first and secondpositions by means of two pins with indents which act against a springloaded ball bearing which indexes the position of the plate with respectto the main body of the cutting block.

According to a first aspect of the invention, there is provided acutting block for fixing relative to a bone for guiding a saw bladeduring a step in an orthopaedic surgical procedure in which the bone iscut, the cutting block comprising:

a. a body having a top surface for guiding a saw blade,b. a top plate which is connected to the body and which can move betweena first position in which the top plate is spaced apart from the bodyand a second position in which the top surface of the top plate iscontiguous with and an extension of the top surface of the body,

-   -   in which the top plate has first and second resiliently        deformable arms extending from it, spaced apart along the top        plate, and in which the body has first and second recesses        formed in it extending substantially perpendicularly to the top        surface of the body, in which the first and second arms on the        top plate can be received so that the arms and the recesses        define the path for movement of the top plate relative to the        body between the first and second positions,    -   and in which each of the recesses has a profiled surface against        which the respective deformable arm acts during movement of the        top plate relative to the body between the first and second        positions so as to cause the arm to deform, the deformation of        each of the arms being greater when the top plate is in an        intermediate position between the first and second positions        than when it is in each of the first and second positions, so        that the top plate is biased away from the intermediate position        towards the first and second positions.

The biasing of the arms to the first and second positions locks the topplate in either the first or second positions.

Providing a cutting block with the features provide for easiermanufacturing, particularly as the numbers of components is reduced.Furthermore, it reduces the need for welding with the attendant heatdistortion that can affect the final product. The cutting block is alsoeasier to clean

Each of the first and second arms may have a pin extending transverselyfrom it, and in which the profiled surfaces are acted against by thepins.

Each of the profiled surfaces may be provided by a groove which is cutin a wall of the body.

The provision of the pins on the arms and which are retained in groovesmeans that, should the arms become removed from the top plate, they areretained within the cutting block and do not become dislodged and findthemselves becoming lodged in surrounding tissue.

Each of the grooves may be curved when viewed in the direction which isdefined by the pin which slides in the groove.

Alternatively, the grooves may have a V-shaped configuration, or may besubstantially linear and provided with indents at either end to retainthe pins at either end of the groove.

As a further alternative, the grooves may be provided with a ridgedprofile to retain the pins at either end of the groove.

The recesses may be shaped so that each of the arms within its recess inthe body is exposed, allowing a user to apply force to the arm to causethe arm to be deformed resiliently to facilitate movement of the topplate between its first and second positions.

The arms may be provided with buttons at the distal end against whichmanual pressure may be made to deform the arms. The buttons may have aridged surface to assist with manual purchase against the buttons.

The top surface may have a raised lip and a pair of projectionsconfigured to define an inner guiding surface.

The top surface may have a recess configured to accommodate the raisedlip and a pair of apertures configured to receive respective ones of thepair of projections.

According to a another aspect of the invention, there is provided acutting block for fixing relative to a bone for guiding a saw bladeduring a step in an orthopaedic surgical procedure in which the bone iscut, the cutting block comprising:

a. a body having a top surface for guiding a saw blade,b. a top plate which is connected to the body and which can move betweena first position in which the top plate is spaced apart from the bodyand a second position in which the top surface of the top plate iscontiguous with and an extension of the top surface of the body,

-   -   in which the top plate has first and second resiliently        deformable arms extending from it, spaced apart along the top        plate, and in which the body has first and second recesses        formed in it generally transverse to the top surface of the        body, in which the first and second arms on the top plate can be        received so that the arms and the recesses define the path for        movement of the top plate relative to the body between the first        and second positions,    -   and in which each of the recesses has a profiled surface against        which the respective deformable arm acts during movement of the        top plate relative to the body between the first and second        positions so as to cause the arm to deform, the deformation of        each of the arms being greater when the top plate is in an        intermediate position between the first and second positions        than when it is in each of the first and second positions, so        that the top plate is biased away from the intermediate position        towards the first and second positions.

The invention will now be described, by way of example only, withreference to the following drawings, of which:

FIG. 1 is a schematic perspective view a cutting block of the invention;

FIG. 2 is a front view of the cutting block of FIG. 1;

FIG. 3 is a corresponding figure to Figure showing the top plate in aclosed position;

FIG. 4 is a rear view of the cutting block of FIG. 1;

FIG. 5 is a side view of the cutting block of FIG. 1 in the direction ofarrow V in FIG. 2;

FIG. 6 is a front view of the body of the cutting block of FIG. 1;

FIG. 7 is a side view of the body of FIG. 6 in the direction of arrowVII;

FIG. 8 is a front view of the top plate of the cutting block of FIG. 1;

FIG. 9 is a side view of the top plate of FIG. 8 in the direction ofarrow IX;

FIG. 10 is cross-section through the cutting block of FIG. 1, in thedirection of arrows X-X′ of FIG. 2;

FIG. 11 is a cross-section in the direction of arrows XI-XI′ of FIG. 2;and

FIG. 12 schematically illustrates the positioning of the cutting blockof FIGS. 1 to 11 in place on the distal end of a femur.

A cutting block 1 comprises a body 2 and a top plate 3.

The body 2 comprises a contoured front face 4, a substantially planarrear face 5, and a top surface 6.

The body 2 includes a main portion 9 with two side portions 10, 11extending laterally from each side of the main portion 9. The sideportions 10, 11 define respective side faces 17, 18 of the body 2.

The body 2 has a plurality of pairs of spaced apertures 7 a, 7 bprovided in the front face 4 in the main portion 9 with correspondingpairs of spaced apertures 8 a, 8 b provided in the rear face 5. Thepairs of spaced apertures 7 a, 7 b; 8 a, 8 b are used to receive a pairof pins 38 to secure the cutting block 1 to the femur 40 as illustratedin FIG. 12 and known to persons skilled in the art.

The main portion 9 of the body 2 has a raised lip 12 on the top face 6which extends substantially orthogonal to the top surface 6.

The top surface 6 also has a pair of substantially oval-shaped raisedprojections 13, 14 protruding from the top face 6.

The lip 12 and raised projections 13, 14 define an inner guiding surface39 used to guide a saw or other cutting tool during distal femoralresection.

Each of the side portions 10, 11 have a substantially U-shaped recess15, 16 provided therein. Each U-shaped recess 15, 16 opens into the topsurface 6 and respective side faces 17, 18 and is generally transverseto the top surface 6 so that they extend substantially perpendicularlyto the top surface 6.

Each side portion 10, 11 has a pair of opposed curved grooves 19 a, 19b; 20 a, 20 b, one curved groove of each pair of curved grooves 19 a, 19b; 20 a, 20 b being provided in the respective front face 4 and rearface 5 of the body 2. Each curved groove 19 a, 19 b; 20 a, 20 b extendsthrough into the respective recess 15, 16. The ends of each groove 19 a,19 b; 20 a, 20 b define stop surfaces to limit movement of the top plate3 between first and second positions as will be described in furtherdetail below.

The top plate 3 has an upper face 21 and a lower face 22. The top plate3 has a front edge 23, rear edge 24 and side edges 25, 26 which areconfigured such that the outer contour of the top plate 3 substantiallymatches the top face 6 of the body 2.

The top plate 3 has a recess 27 along the front edge 23 configured toaccommodate the raised lip 12 of the body 2. The top plate 3 also has apair of first and second substantially oval-shaped apertures 28, 29configured to receive respective protrusions 13, 14 of the body 2. Inthis way, the top plate 3 can be moved to a position in which it iscontiguous with, and an extension of, the top surface 6 of the body 2.In this position the upper surface 21 of the top plate 3 defines adistal surface 37 for the cutting block 1.

A circular aperture 30 is provided in the top plate 3 between the firstand second apertures 28, 29.

Extending orthogonally from the lower face 22 of the top plate 3 spacedapart along the top plate 3, towards the side edges 25, 26, are firstand second resiliently deformable arms 31, 32. The resilientlydeformable arms 31, 32 terminate in a button 33, 34 which serve tofacilitate manual deformation of the arms 31, 32 as will be described infurther detail below.

Extending transversely, and in opposite directions, from each of thefirst and second arms 31, 32 area pair of pins 35 a, 35 b; 36 a, 36 b.

The first and second resiliently deformable arms 31, 32 are connected tothe top plate 3 by means of a living hinge connection or other suitablemeans of enabling the deformation.

When assembled, the cutting block 1 comprises the top plate 3 engagedwith the body 2. Specifically, the first and second resilientlydeformable arms 31, 32 are received in the respective recess 15, 16 andthe pins 35 a, 35 b; 36 a, 36 b are received into, and engage with,corresponding grooves 19 a, 19 b; 20 a, 20 b. The pins 35 a, 35 b; 36 a,36 b are arranged to slide within, and along the length of, the groove19 a, 19 b; 20 a, 20 b with which it is engaged.

The grooves 19 a, 19 b; 20 a, 20 b define profiled surfaces of therespective recess 15, 16, and by virtue of engagement of the pins 35 a,35 b; 36 a, 36 b in the grooves 19 a, 19 b; 20 a, 20 b, the resilientlydeformable arms 25, 26 act against these profiled surfaces.

The resiliently deformable arms 25, 26 and the recesses 15, 16 intowhich they are received define a path for movement of the top plate 3relative to the body 2 between a first and a second position as will bedescribed further below.

In the first position the top plate 3 is spaced apart from the topsurface 6 of the body 2 and the pins will be located within therespective groove at a first end of the groove 19 a, 19 b; 20 a, 20 b.This is illustrated in FIG. 2.

In the second position, the top plate 3 is contiguous with, and anextension of, the top surface 6 of the body 2 and the pins 35 a, 35 b;36 a, 36 b will be at the other, second, end of the respective groove 19a, 19 b; 20 a, 20 b. In the second position, the raised lip 12 of thebody 2 is received within the recess 27 of the top plate 3, and thefirst and second substantially oval-shaped apertures 28, 29 receiverespective protrusion 13, 14 of the body 2. In this way, the uppersurface 21 is flush with respective protrusions 13, 14 and the top ofthe raised lip 12 to define the distal surface 37. This is illustratedin FIG. 3.

The ends of the grooves 19 a, 19 b; 20 a, 20 b define the stop surfaceslimiting movement of the top plate 3 between the first and secondpositions.

Movement of the top plate 3 relative to the body 2 between the first andsecond positions causes the resiliently deformable arms 25, 26 to deformas the pins 35 a, 35 b; 36 a, 36 b act against the profiled surfacesdefined by the grooves 19 a, 19 b; 20 a, 20 b.

As the grooves 19 a, 19 b; 20 a, 20 b are curved, the deformation ofeach of the arms 25, 26 is greater when the top plate 3 is in anintermediate position between the first and second positions than whenit is in each of the first and second positions. Thus, the top plate 3is biased away from the intermediate position towards the first andsecond positions. In this way, the top plate 3 is biased to either thefirst position or second position so as to remain that position whenmoved to that position.

To move the top plate 3 between the first and second positions, the topplate 3 is gripped manually and moved between the two positions.

This can be further facilitated by applying manual pressure to thebuttons 33, 34, for example by means of a finger and the thumb of onehand, which causes the arms 25, 26 to deform inwardly towards each otherfacilitates sliding of the pins 35 a, 35 b; 36 a, 36 b in the grooves 19a, 19 b; 20 a, 20 b so that the top plate 3 moves between the firstposition and the second position.

The cutting block 1 of the present invention is for use in kneereplacement surgery.

In accordance with known techniques for knee replacement surgery, bonesurfaces require preparation in order for the replacement prosthetic tobe attached. One of the bone surfaces that require preparation is thedistal end of a femur at the knee. The cutting block of the presentinvention is used in the distal femoral resection step.

In order to carry-out the distal femoral resection, the distal cuttingblock 1 is mounted onto the distal end of the femur.

Prior to distal femoral resection, anterior and posterior portions,specifically the anterior cortex and the posterior femoral condyles, ofthe femur are resected in accordance with known techniques.

The cutting block 1 is then mounted on the resected surface of theanterior cortex in order to carry out the distal femoral resection. Tomount the distal cutting block 1 onto the distal section of the femur, adistal femoral outrigger is used. An example of this as the distalfemoral outrigger of the LCS® Complete™—P.F.C. Sigma™ RP Mobile BearingTotal Knee System manufactured by DePuy Orthopaedics Incorporated.

The distal cutting block 1 is attached to the distal femoral outriggerby means of an attachment mechanism (not shown) which is retained withinthe circular aperture 30 of the top plate 3. This means of attachment isknown to persons skilled in the art and need not be described in anyfurther detail herein.

At this stage, the top plate 3 of the distal cutting block 1 is in thefirst position, the top plate being moved to this position by manualforce applied to the top plate 3 and with further manual pressureapplied to the buttons 33, 34 if required.

Because the grooves 19 a, 19 b; 20 a, 20 b are curved and thedeformation of the arms 25, 26 is at its least when at the ends of thegrooves 19 a, 19 b; 20 a, 20 b, the top plate 3 is biased and retainedin this first position.

A distal femoral alignment guide is placed into the notch of the femurand the distal femoral outrigger inserted into the alignment guide sothat the distal cutting block 1 abuts and rests on the resection portionof the anterior cortex. When the distal cutting block 1 is flat on theanterior cortex, the cutting block 1 is pinned onto the femur by meansof the pins 38 inserted through the relevant pin holes 7 a, 7 b; 8 a, 8b and into the bone of the femur 40 in accordance with known surgicaltechniques. The distal femoral outrigger is the removed from the distalfemoral alignment guide and distal cutting block 1.

The alignment guide and outrigger are known devices and, in so far asthey do not form part of the present invention, need not be described inany further detail herein. The use of alignment guides and outriggers inknee replacement surgery is described, for example, in “LCS® SurgicalTechnique” Product Information Sheet by De Puy International and dated2010.

Before the distal femoral resection can be carried out the extension gapbetween the femur and the tibia needs to be assessed.

To do this, the top plate 3 of the distal cutting block 1 needs to bemoved to the second position. This is achieved, again by manual pressureon the top plate 3 and by use of the buttons 33, 34, if required. Thedistal surface 37 of the cutting block 1 now represents the level of thecut for the distal femoral resection and can be used to assess theextension gap when used fully extended.

This extension gap must equal the flexion gap and this is done using aspacer block (not shown) in accordance with known techniques. If thespacer block is parallel and aligns with the tibial cut while medial andlateral tissues are equally tensioned then the distal cutting block 1 iscorrectly located.

The distal cutting block 1 can be positioned using a different row ofholes 7 a, 7 b; 8 a, 8 b to resect a greater or lesser amount of distalfemur to ensure the spacer block will fit in the extension gap. Once thedistal cutting block 1 is in the correct position then distal femoralresection can be carried out.

In order to carry-out the resection, the top plate 3 can be in the firstposition or the second position depending upon which guide surface 37,39 the surgeon has chosen to use—either the distal surface 37 or theinner guiding surface 39. Again, this is achieved by manual pressureapplied to the top plate 3 and buttons 33, 34 as required.

The resection is performed using a saw blade inserted through the gapbetween the top plate 3 and the cutting block body 2 if the innerguiding surface 39 is being used by the surgeon; otherwise the surgeonuses the distal surface 37 as the surface to guide resectioning of thefemur.

Once the resection has taken place, then the cutting block 1 can beremoved.

1. A cutting block for fixing relative to a bone for guiding a saw bladeduring a step in an orthopaedic surgical procedure in which the bone iscut, the cutting block comprising: a. a body having a top surface forguiding a saw blade, b. a top plate which is connected to the body andwhich can move between a first position in which the top plate is spacedapart from the body and a second position in which the top surface ofthe top plate is contiguous with and an extension of the top surface ofthe body, in which the top plate has first and second resilientlydeformable arms extending from it, spaced apart along the top plate, andin which the body has first and second recesses formed in it extendingsubstantially perpendicularly to the top surface of the body, in whichthe first and second arms on the top plate can be received so that thearms and the recesses define the path for movement of the top platerelative to the body between the first and second positions, and inwhich each of the recesses has a profiled surface against which therespective deformable arm acts during movement of the top plate relativeto the body between the first and second positions so as to cause thearm to deform, the deformation of each of the arms being greater whenthe top plate is in an intermediate position between the first andsecond positions than when it is in each of the first and secondpositions, so that the top plate is biased away from the intermediateposition towards the first and second positions.
 2. The cutting block ofclaim 1, in which each of the first and second arms has a pin extendingtransversely from it, and in which the profiled surfaces are actedagainst by the pins.
 3. The cutting block of claim 2, in which each ofthe profiled surfaces is provided by a groove which is cut in a wall ofthe body.
 4. The cutting block of claim 3, in which each of the groovesis curved when viewed in the direction which is defined by the pin whichslides in the groove.
 5. The cutting block of claim 1, in which therecesses are shaped so that each of the arms within its recess in thebody is exposed, allowing a user to apply force to the arm to cause thearm to be deformed resiliently to facilitate of the top plate betweenits first and second positions.
 6. The cutting block of claim 1, whereinthe top surface includes a raised lip and a pair of projectionsconfigured to define an inner guiding surface.
 7. The cutting block ofclaim 6, wherein the top surface includes a recess configured toaccommodate the raised lip and a pair of apertures configured to receiverespective ones of the pair of projections.